The present invention relates to an image forming system for recording images using electrophotographic developing processes, and more particularly, to a method for automatically eliminating a paper jam.
Electrophotographic developing processes are widely used in copiers, printers, facsimile machines and other instruments to generate an image corresponding to an electrical signal. An example of an electrophotographic developing printer is a laser beam printer (hereinafter referred to as "LBP"). The general structure of a LBP using the electrophotographic developing process is disclosed in detail in U.S. Pat. No. 5,002,266 entitled "Sheet Feed Apparatus for Image Forming System" issued to Kikuchi et al. on 26 Mar. 1991.
When a paper jam occurs within an image forming system, elimination of the jam is often enabled through rotation of drive rollers within the system. In U.S. Pat. No. 5,257,070 entitled Selective Control Of Distributed Drives To Maintain Interdocument Gap During Jam Recovery Purge, issued to Miller et al. discloses a scheme where the paper path is divided into a plurality of zones. During a paper jam, copy sheets are systematically purged from various zones of the paper path in a predetermined order based upon the particular disposition of the copy sheets in the paper path zones. Many conventional devices utilize paper jam eliminating methods similar to Miller et al. With these methods, however, there can be problems with toner contamination. That is, while jammed paper is ejected from the system, developing material, such as toner, can contaminate the interior of the image forming system.
The problem of toner contamination has been recognized in U.S. Pat. No. 4,878,428 entitled Control Method Of Transporting A Cut Sheet In A Printing Station And Apparatus Using The Same, issued to Watarai. This art discloses steps of: detecting a paper jam within a feeding unit, stopping operation of a transfer mechanism within the feeding unit, continuing to operate other transfer mechanism within the printer until all unjammed paper is ejected, and then stopping operation of all transfer mechanism. Although Watari '428 purports to avoid the toner contamination problem discussed above, it has a disadvantage of not promptly ejecting the paper jammed within the feeding unit. Accordingly, toner contamination is avoided, but a paper jam elimination problem still exists.